In the 1950's, the wiring of electrical components within an electrical system was vastly simplified by the introduction of printed circuit boards. These boards generally utilized a nonconductive base, such as phenolic, upon which conductive ribbons or strips, such as copper, could be placed for making electrical connections between plated through holes in which the leads of the electrical components were inserted and electrically connected by solder. Since that time, many improvements have been made in the methods of manufacturing printed circuit boards and the techniques for joining electrical components thereto.
As this development continued, the electrical connector art also improved. Screw machine contacts that had to be soldered on to electrically conductive wires were replaced with stamped sheet metal contacts which could be crimped on to a conductive wire after the insulation thereon had been stripped from the end thereof. These sheet metal contacts were often designed for insertion into insulated electrical connectors which were then connected to the printed circuit boards. In some applications, however, it became possible to connect conductive wire directly to the component without the need for a separate electrical connector. Thus, the integral contact itself became the electrical connector system.
Examples of integral electrical contacts which are used to connect a conductive wire directly to the conductive strip upon a printed circuit board may be found in U.S. Pat. No. 2,980,878 by R. C. Swengel and U.S. Pat. No. 3,079,578 also by R. C. Swengel. Each of the Swengel patents discloses a contact having a pair of J-shaped edges wherein the outermost tip of the shorter leg of the J frictionally engages the conductive ribbon upon the printed circuit board. The contacts described within the Swengel patents work well for low voltage signals such as those generally encountered on the conductive strips of a printed circuit board. However, over a period of time the single edge contact begins to corrode due to atmospheric contamination thus increasing the resistance between the contact and the conductive ribbon.
Another example of a specially designed integral sheet metal contact which acts as an electrical connector system for connecting a conductive wire to the chassis of an electrical housing is shown in U.S. Pat. No. 3,535,673 by F. J. Maltais and W. W. Loose. Other variations of this ground terminal are shown in U.S. Pat. No. 3,686,609 by W. A. Hansen and U.S. Pat. No. 3,910,663 by J. L. Winger. Each of these ground terminals utilize serrated edges to ensure good electrical contact between the terminal and the housing in which it is inserted. Clearly, removal and insertion of the ground terminal over a period of time will cause wear of the serrated edges and deteriorate the electrical connection between the terminal and the housing in which the terminal is inserted.
As the techniques for mounting electricl components upon printed circuit boards has improved, the components have been mounted closer together thus increasing the problem of electrical interference and the need for a good ground connection. Many electrical packaging systems have thus begun to incorporate ground planes which are large sheets of conductive material, such as aluminum. These ground planes may be interspersed among the printed circuit boards to provide good electrical grounding.
Over the life of an electrical system in which a ground plane is used, connection with that ground plane may be made and broken many times. Thus, an electrical connector system associated with a typical ground plane must be highly reliable, have a long life, and introduce a minimum amount of electrical resistance between the ground plane and the conductive element connected thereto.